An organic electroluminescence (EL) device is regarded as a promising solid-emitting large-area full color display device, and various developments have been conducted so far. In general, an organic EL device comprises an emitting layer and a pair of opposing electrodes that sandwich the emitting layer. When an electrical field is applied between the both electrodes, electrons are injected from the cathode and holes are injected from the anode. Further, these electrons are re-combined with the holes in the emitting layer, create an excited state, and energy is emitted as light when the excited state is returned to the ground state.
Conventional organic EL devices had a high driving voltage as compared with inorganic emitting diodes, and hence, the luminance and the luminous efficiency were low. In addition, conventional organic EL devices suffered significant deterioration in properties, and hence, practical application thereof has not been realized yet. Although gradual improvements have been attained in recent organic EL devices, there is an increasing demand for further improvements in luminous efficiency or the like.
With improvements in organic EL emitting materials, performance of an organic EL device has been gradually improved. Improvement in luminous efficiency in an organic EL device is an important subject that leads to lowering in consumption power or improvement in durability of a display. Although improvements have been attained by various researches so far, further improvements have been required.
In order to solve these problems, Patent Documents 1 to 6 disclose an organic EL device in which an anthracene derivative having dibenzofuran as a substituent is used as an emitting material.
Further, Patent Documents 4, 7 to 11 disclose an emitting material having a naphthobenzofuran structure or a naphthobenzothiophene structure. Although use of these materials leads to improvement in luminous efficiency, further improvement in efficiency has been required.